The present invention relates to differential pressure sensors. More specifically, the present invention relates to differential pressure sensors which measure pressure based upon diaphragm deflection.
Pressure sensors are used to measure pressures. A differential pressure sensor is configured to respond to a differential pressure, that is, the difference between two pressures.
One technique which is used to measure differential pressure is through a deflectable diaphragm. A first pressure is applied to one side of the diaphragm and a second pressure is applied to the other side of the diaphragm. The deflection of the diaphragm is proportional to the difference between the two applied pressures. Diaphragm deflection can be measured by configuring the diaphragm so that it acts as a plate of a capacitor. The capacitance of the diaphragm assembly changes based upon the diaphragm position. Therefore, capacitance can be related to diaphragm position which in turn is representative of the differential pressure applied to the diaphragm.
Pressure sensors frequently operate in harsh environments. Such environments can cause failure in highly accurate pressure sensors which tend to be quite delicate. One technique which has been used to isolate the pressure sensor is to isolate the pressure sensor from the fluid (also called xe2x80x9cprocess fluidxe2x80x9d) whose pressure is being measured. One such technique uses an isolation diaphragm in which process fluid is on one side of isolation diaphragm and isolation fluid is on the other side. The isolation fluid contacts the pressure sensor diaphragm. As the process fluid pressure changes, the isolation diaphragm, responsively deflects which causes the change in pressure to be transferred through the isolation fluid to the sensor diaphragm. However, the isolation fluid in the diaphragm can introduce errors in pressure measurements and can be altered over time or due to application of heat or other external influences. Further, the fluid can leak with time which can result in reduced fluid volume or fill fluid which has been contaminated by process fluid.
A pressure sensor is provided for measuring a pressure difference between two fluids which does not require isolation fluid. The pressure sensor includes a diaphragm support member having an outer periphery and diaphragms coupled thereto. Movement of the diaphragms are the movement of a moveable member. The movement can be sensed to determine the applied differential pressure. The coupling member is joined to the outer periphery with a web. The web is recessed from opposed outwardly facing surfaces of the outer periphery, and first and second diaphragms disposed on opposite sides of the diaphragm support member. Each diaphragm is joined to the outer periphery and to the coupling member.